Monday, November 25, 2013

Graphene make light work - a boon for optoelectronic applications of graphene

Graphene (Ms. G, as I call it QUEEN of 2D materials :-) ) , since 2004, has demonstrated her acrobatism with number of applications in various fields viz. transparent and flexible electronics, touch screens etc. Now, graphene has been demonstrated as a infrared photodetector which can convert light signals to electrical signals. This makes graphene the leading material so far which can be used for electrical as well as optical applications.

Wednesday, November 20, 2013

Polycrsytalline graphene is as strong as single crystalline graphene!

Good news for mechanical applications of graphene - 

Researchers have measured the intrinsic strength of single crystal and bicrystal graphene grown using chemical vapor deposition. They have found that polycrystalline graphene with high angle grain boundaries are as strong as single crystal graphene. The high strength is attributed to the atomic-scale strain fields, determined by a transmission electron microscope, in the carbon-carbon bonds at the boundary.

Graphene nanoribbons (GNRs) grown using PMMA !

Graphene nanoribbons (GNRs) are very promising material for electronic applications as quantum confinement opens a band gap in gapless graphene. Now researchers have used PMMA, a polymer used as a support to transfer graphene, to grow GNRs on epitaxial Ni thin films. The study paves for controlling the orientation of GNRs.

Tuesday, November 19, 2013

We all get confused by the name "graphene" as it has now become a routine to use the word for many 2D carbon materials which actually are not real "graphene". One can have a look at the following article which provides a recommended nomenclature for 2D carbon materials. Its a must read for newcomers and a guide for those who are already in the field.

Monday, November 18, 2013

"Graphene Handbook" is in the market now. I think its first of its kind. The chapters in the book spans from graphene fundamentals to its market commercialization.

Thursday, September 12, 2013

Controlling number of Dirac points in graphene- Band structure engineering

Researchers from India have demonstrated control on the number of Dirac points in graphene by using a superlattice structure. The work is promising in controlling not only the electronic but magnetic and thermo-electric properties of graphene as well.

Sunday, June 16, 2013

Dual gated bilayer graphene shows photothermal response

Graphene is seen as a potential candidate for photodetection applications. Now, the researchers have studied dual gated bilayer graphene to observe the gating effect on its photothermal response. They have found a significant role of hot electron thermal relaxation in defining the photovoltaic response of graphene.

Multilayer graphene shows temperature dependence of far-infrared response

Graphene possesses miracle optical properties with exhibition of broadband transmission irrespective of the wavelength of light. However, researchers have found a temperature dependence of far-infrared response of epitaxial multilayer graphene. The results are vital for graphene based devices.

Flexible graphene radio frequency devices

The mechanical strength of graphene allows one to fabricate flexible devices. The researchers have now demonstrated flexible graphene radio frequency devices with cut off frequencies as high as 10 GHz with a temperature stability upto 400 K.

Monday, May 20, 2013

Graphene is making physics richer !

Graphene crystallographically aligned on boron nitride flakes is found to exhibit second generation Dirac points and reversal of Hall effect. Cloning of Dirac points is observed under high magnetic field leading to third generation Dirac points. The results pave way for controlling the electronic structure of graphene in superlattice configurations.

Thursday, May 16, 2013

Photoresponsive graphene

It is known that graphene has no band gap and hence does not exhibit photoreponse. However, by band structure engineering, one can open up the band gap. In a recent report, researchers have obtained a high photoresponsivity of around 8 A/W in monolayer graphene by creating electron trapping centres. The results pave way for optoelectronic applications of graphene.

Wednesday, May 1, 2013

Mie scattering analog in graphene

It is proved theoretically that Dirac electron wave in graphene can be manipulated similar to Mie scattering of light on small particles. It is realized by using circular gating region in graphene which acts as a quantum dot.

Negative differential conductance in graphene transistors

Graphene's low density of states have been utilised for resonant tunneling through a boron nitride film and negative differential conductance in graphene transistors. The device is comprised of a few layer thick boron nitride layer sandwiched between graphene layers. The few atomic thick device promises to have ultrafast transient times.

Thursday, April 18, 2013

Graphene nanostructures- a promised plasmonic platform for mid-infrared region

The investigation of the pathways by which plasmon, a quanta of collective oscillations of electrons, loses energy is very important for plasmonic science and technology. Graphene plasmonic structures in this direction are very helpful. Researchers have used CVD graphene nanostructures to understand the damping of plasmons in graphene and observed that substrate plays a vital role in significant plasmon dispersion and damping.

Tuesday, April 16, 2013

Loudspeakers made out of graphene

Chemical vapor deposited graphene has been used to make an audio device where graphene coated PVDF film can emit sound waves in a range of frequencies with high sound pressure level and low harmonic distortion. This demonstrates that graphene has uses which one has to think. The results are published in Applied Physics Letters:

Tuesday, April 2, 2013

A graphene based hot electron transistor

In a recent study published in Nano Letters, experimentalists have demonstrated DC functionality of graphene based hot electron transistor. Moreover, the device is integrated using fabrication steps which are compatible with Si technology. An on/off ratio exceeding 10E4 is reported for graphene based transistor.
The findings open doors for graphene device market.

Hot carrier generation in graphene !

In a recent study, researchers have analyzed different pathways contributing to the ultrafast relaxation of photoexcited carriers in graphene using tetra-hertz pump spectroscopy. The results indicate that carrier-carrier scattering is the dominant mechanism leading to the generation of hot electrons in graphene. These hot carriers in turn can drive current in graphene enabling its high efficiency optoelectronic applications.

Electron optics applications of graphene

Transverse magnetic focusing has been observed in graphene and is expected to open new application area of graphene in electron-optics. In a recent report published in Nature Physics, researchers have used ambipolar nature and ballistic transport properties of graphene to study the transverse magnetic focusing effect upto room temperature.

Thursday, March 28, 2013

Graphene used as a platform to observe atomic collapse

Researchers have imaged atomic collapse in Ca dimers placed on CVD graphene/BN stack using STM. This became possible because charge carriers in graphene behave as massless relativistic particles.

Wednesday, March 20, 2013

Graphene devices go for integration with Si- A new approach

The quest is on for integrating graphene with Si and is a dreamwork for nanoelectronics. In this direction, researchers have developed a new 'manufacturable process integration' (MPI) approach for fabricating graphene devices. The approach can be a significant milestone to enter in the era of nanoelectronics based on 2D materials.

New study unleashes photovoltaic potential of doped graphene

Optoelectronic properties of graphene have shown great promise in next generation photovoltaic devices and photodetectors. A recent study, published in Nature Physics, reveals the highly efficient conversion of light into free electron-hole pairs through tetrahertz probe measurements. The results are very promising and enable great future for highly efficient optoelectronic applications of graphene.

Just for new experimentalists :-)

It's a long time, I have blogged new results on graphene as I was bit busy. To give it a start, I am providing a link ( I know u can it from Google also..) where one can find excerpts from an interview (2010) with K. Novoselov. This is just to encourage students for doing experiments and implementing any idea they come across.
Just do it..

Sunday, January 27, 2013

Multifunctional crumpled and folded graphene !

In a recent report in Nature, researchers have demonstrated controlled crumpling and folding of CVD graphene for utilization in various electronics, biomedical, energy and composite applications. 
The approach is very simple and effective.

Pure bulk valley current in graphene !

A scheme for generating large valley currents in graphene mechanical resonators in the suspended regions is reported. 
The work is a progress towards utilizing the valleytronics of graphene.

Spin gating of graphene by proximity effects

Frist principle calculations studies has revealed the significance of proximity effects of a magnetic insulator, europium oxide, on graphene spin related properties. Large spin polarization around 24 % and exchange-splitting band gap around 36 meV are reported.

Thursday, January 24, 2013

Graphene plasmonics helps in detecting drug cheaters!

Another breakthrough from the "Noble winners of graphene discovery" can help in beating the drug cheaters.  Based on reversible hydrogenation of graphene, scientists create a plasmonic metamaterial which has potential for label free biosensing.

Graphene oxide goes for radioactive nuclides!

Graphene oxide, a derivative of graphene, is found to have potential to capture some of the human made radiactive nuclides from sea water.
This is a great breakthrough !

Wednesday, January 23, 2013

Graphene project wins European funds !

Given graphene's unlimited applications, it is not surprising that a graphene project has won European funds in billion. The application sought will be batteries, sensors and computing.

Tuesday, January 22, 2013

Health risks of graphene

Given its wide applications, graphene will be used extensively and is definitely going to be a part of our ecosystem. Therefore, it is mandatory to understand the health risks of graphene for a precaution. 
In a current review article, possible health risks of graphene associated with its shape, size and structures are provided.

Graphene a super gas barrier !

Super gas barrier thin films, fabricated with layer-by-layer assembly of polyethylenimine and graphene oxide, exhibit significantly reduced oxygen and carbon dioxide transmission rates. This thin film's nanobrick wall structure also provides high gas selectivity for hydrogen.

Sunday, January 20, 2013

Dirac Fermions in graphene do a lot- Ratchet effect !

In a recent Nature article, researchers have demonstrated magnetic ratchet effect in graphene under the application of THz radiation which results in transformation of a.c. power to dc currents. 
Sounds interesting !

Tuesday, January 15, 2013

Plasmon transport in graphene

We have heard of charge transport of graphene and its control by external electrical biasing. In a recent work published in Nature Communications, a charge pulse travelling in plasmon mode in graphene to the GHz range can be modulated by applying an external magnetic field. The study paves way for further plasmonic applications of graphene in a controlled manner.

Graphene can be band-engineered for photonic appliations !

In a new published research, complete or quasi collapse of conduction and valence quasi bands of ac-driven graphene is demonstrated using optical waveguides.

I still need to go through the article :-)

CVD graphene as a biosensing platform

In a recent work, reserachers have used Hall measurements to understand the interaction of DNA with graphene to gain further insights in the process. This brings a step forward in using graphene as a bio-sensor for biological applications.

Sunday, January 13, 2013

Micro-wave-chemical vapor deposition of graphene walls

Microwave plasma CVD is used to grow vertically standing graphene walls which can be utilised as field emitters. The technique holds promise to grow graphene at low temperatures.

Sunday, January 6, 2013

Nanoscale Radiative Heat Flow due to Surface Plasmons in Graphene and Doped Silicon

Owing to its two-dimensional electronic structure, graphene exhibits many unique properties. One of them is a wave vector and temperature dependent plasmon in the infrared range. Theory predicts that due to these plasmons, graphene can be used as a universal material to enhance nanoscale radiative heat exchange for any dielectric substrate. Here we report on radiative heat transfer experiments between SiC and a SiO2 sphere that have nonmatching phonon polariton frequencies, and thus only weakly exchange heat in near field. We observed that the heat flux contribution of graphene epitaxially grown on SiC dominates at short distances. The influence of plasmons on radiative heat transfer is further supported with measurements for doped silicon. These results highlight graphene’s strong potential in photonic near field and energy conversion devices.

Carrier Drift Velocity and Edge Magnetoplasmons in Graphene

In a fundamental study using exfoliated graphene, the researchers investigate electron dynamics at graphene edge by studying the propagation of collective edge magnetoplasmon excitations.

Electrical Control of Silicon Photonic Crystal Cavity by Graphene

Efficient conversion of electrical signal to optical signal in nano-photonics enables solid state integration of electronics and photonics. In a recent work, cavity resonance of a Si photonic crystal cavity covered by graphene is significantly changed.

Thursday, January 3, 2013

Vertical field effect transistor based on graphene-WS2 heterostructures

It is well demonstrated that graphene, a 2D atom thick sheet, has the potentials to bring revolution in electronic industry. With the development of other 2D materials like h-BN and transistion metal dichalcogenides like MoS2, WS2, the graphene applications can be truly realized.  
Taking another leap in this direction, researchers have demonstrated a flexible vertical field effect transistor based on graphene-WS2-h BN heterostructures which is a proof of concept device.

Tuesday, January 1, 2013

3D freestanding graphene-MnO2 composite for supercapacitor applications

CVD grown graphene on Ni foam yields a nice 3D graphene network. Researchers have loaded this structure with MnO2 and converted it into an active material  for supercapacitor applications.

Band gap engineered CVD graphene

We have successfully opened up band gap in CVD grown graphene by in-situ BN doping. A band gap of around 0.6 eV is opened. The present work paves way for graphene based technology where band gap is needed.